Patent GB-271927-A (GB)
Title: Improvements in or relating to the measurement of the rate of and total feed of solid materials
IPC: G01F13/00
Filed: 1926-01-30
Abstract: 271,927. Bursill, A., and Electroflo Meters Co., Ltd. Jan. 30, 1926. Feed of granular materials, measuring.-Means for measuring by an electric method the rate and total feed of granular material such as the consumption of coal by a boiler fed by a chain grate stoker comprises a centrifugal device having a body of conducting liquid adapted on rotation of the device by the conveyer to vary an electrical resistance connected in circuit with the indicating instruments and with a potential divider controlled or controlling the thicknes of the layer of material. In the form shown in Fig. 1, the centrifugal device comprises a cylinder 1 of insulating material mounted on a spindle 2 driven by the conveyer and having a series of nickel or other contacts 3 projecting into the interior and attached at their outer ends to resistance coils 4 wound on the cylinder. The cylinder contains a quantity of mercury 5 electrically connected through the metal base 6 of the cylinder, the spindle 2 and a brush 7 to a terminal 12, the other terminal 13 being connected through a brush 8 and insulated slip ring 9 to the end of the resistance winding. The contacts are arranged at such heights and the resistances of such value that there is a linear relation between the conductivity and the speed of rotation. To modify the current passing in accordance with the opening of the thickness regulator a resistance 26, Fig. 3, is arranged in the circuit, a movable contact 27 controlled by the regulator door 34 being connected in series with the centrifugal device 28. The measuring instruments 39 are shunted across the contact 27 and the end 40 of the resistance 26 and to compensate for the current consumption of the instruments themselves a second contact 41 connected to the opposite end of the resistance 40 and movable over a second resistance is provided. A constant voltage is applied to the circuit by a transformer 33. In a modification, Fig. 4, the instruments are connected in series with the centrifugal device 28 and the potential applied to the circuit is taken from the secondary winding 42 of a transformer 43. Tappings on the secondary are taken to a circular arrangement of contacts 44 which co-operate with a contact arm 45 operatively connected to the regulator door 34, the contact arm 45 having two contacts connected by a resistance 50 to prevent short circuiting. A modified form of centrifugal device is shown in Fig. 2, comprising a container 15 with contact rod's 17 connected to a resistance winding 18, the rods being adapted to be short circuited successively by mercury rising in the container as it is discharged through openings 22 from a rotary pump 14 driven by the conveyer, the mercury being admitted to the pump through apertures 20 from a reservoir 16. According to the Provisional Specification a float operating a choke coil could be substituted for the contact rods. To prevent actuation of the indicating instruments when the supply of material is cut off a switch operated by the hopper door may be provided to open the electric circuit or the potentral divider may be operated by a trailer moved by the material in accordance with its thickness. Specifications 11459/14, 186,661 and 192,126 are referred to.